In a speech Mr Ahmadinejad also promised "very good nuclear news in the coming days" -- just as International Atomic Energy Agency (IAEA) chief Mohamed ElBaradei is scheduled to visit the Islamic republic.
"Be certain that the government which serves you will follow the wishes of the people with wisdom and strength, and will not back down one iota," the hardline president said in a speech carried live on state television.
A military official said the "good news" concerned developments in
enrichment work.
Iran categorically rejects charges that it is seeking atomic weapons and has so far rejected a UN Security Council demand for Tehran to freeze sensitive enrichment work.
Reports dismissed
Mr Ahmadinejad’s comments came amid explosive new reports in the United States saying that President George W Bush is considering military options to knock out the Islamic republic's nuclear program.
The New Yorker magazine reported in its April 17 issue that the
administration is planning a bombing campaign against Iran, including use of bunker-buster nuclear bombs to destroy a key suspected Iranian nuclear weapons facility.
And Sunday's Washington Post reported that Mr Bush is studying options for military strikes as part of a broader strategy of coercive diplomacy to pressure Iran.
President Bush dismissed the reports as "wild speculation", saying the focus remained on a diplomatic solution.
"The doctrine of prevention is to work together to prevent the Iranians from having a nuclear weapon," Mr Bush said in Washington.
"I know we hear in Washington 'prevention means force'," he added.
"In this case, it means diplomacy, by the way. I read the articles in the newspapers this weekend -- it was wild speculation," he said.
White House spokesman Scott McClellan said however that Mr Bush is not taking the military option off the table.
Meanwhile, the deputy head of Iran's atomic organisation, Mohammad Saidi, said an IAEA team was visiting a uranium ore conversion plant at Isfahan and would later visit an enrichment facility at Natanz.
Mr ElBaradei's visit, reportedly due to begin on Wednesday, is his first to the country this year and comes amid growing international pressure on Iran to suspend its uranium enrichment activities -- seen in the West as a cover for weapons development
Enrichment is the process used to manufacture fuel for civil nuclear power stations but can be also be extended to manufacture the fissile core of an atomic bomb.
On March 29, the UN Security Council called on Iran to suspend uranium enrichment to provide a watertight guarantee that its nuclear program is peaceful, and asked Mr ElBaradei to report on Iranian compliance after 30 days.
European Union foreign policy chief Javier Solana said the 25-nation bloc could consider slapping sanctions on Iran, including a visa ban, if current UN-led diplomatic efforts fail.
World oil prices rose on Monday, hovering around US$68 per barrel on market jitters over a potential military conflict between the US and Iran, dealers said.